Plasma and Fusion Research

Volume 14, 2406015 (2019)

Regular Articles

Non-Axisymmetric Radiation from Surface-Wave Oscillator Driven by Weakly Relativistic Electron Beam
Yuta ANNAKA, Kazuo OGURA, Kosuke OZAWA, Makoto NAKASONE and Yuki SATO
Graduate School of Science and Technology, Niigata University, Niigata 950-2181, Japan
(Received 6 September 2018 / Accepted 24 November 2018 / Published 24 January 2019)

Abstract

In this paper, non-axisymmetric radiation from a W-band surface wave oscillator (SWO) is observed. The SWO is based on a cylindrical corrugated waveguide with a periodic structure on its inner wall. This SWO is driven by electron beams with energy of less than 100 keV and a current on the order of 100 A. The waveguide has transverse magnetic (TM) and transverse electric (TE) modes as its axisymmetric normal modes. Non-axisymmetric modes also appear as a hybrid of TM and TE modes and form surface waves near the periodic structure. The frequencies of the non-axisymmetric modes increase as the azimuthal mode number m increases. By injecting an annular electron beam into the SWO, many non-axisymmetric modes with m up to 30 are excited and intense radiation is generated at frequenies up to 140 GHz.

Keywords

terahertz wave source, surface wave oscillator, corrugated waveguide, non-axisymmetric mode

DOI: 10.1585/pfr.14.2406015

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